Field
Embodiments of the present invention relate to apparatus and methods for processing semiconductor substrates. More particularly, embodiments of the present invention provide apparatus and methods for reducing non-uniformity and/or skews during substrate processing.
Description of the Related Art
Electronic devices, such as flat panel displays and integrated circuits commonly are fabricated by a series of process steps in which layers are deposited on a substrate and the deposited material is etched into desired patterns. The process steps commonly include physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced CVD (PECVD), and other plasma processing. Specifically, a plasma process requires supplying a process gas mixture to a vacuum chamber, and applying electrical or electromagnetic power (RF power) to excite the process gas into a plasma state. The plasma decomposes the gas mixture into ion species that perform deposition, etch, implant or other processes.
One problem encountered with plasma processes is the difficulty associated with establishing uniform plasma density over the substrate surface during processing, which leads to non-uniform processing between the center and edge regions of the substrate and non-uniform processing azimuthally within center and edge regions. One reason for the difficulty in establishing uniform plasma density involves gas flow skews due to asymmetry in the physical process chamber design. Such skews not only result in naturally, azimuthal, non-uniform plasma density, but also make it difficult to use other processing variables or “knobs” to control center-to-edge plasma uniformity.
Therefore, a need exists for a plasma processing apparatus that improves gas flow symmetry for improved plasma uniformity control.